The present invention relates generally to the manufacture of ceramic carriers and specifically to those ceramic carriers requiring that certain surface features be accurately located in predetermined locations.
The problem generally addressed by this invention is caused by the fact that much of the process of manufacturing a ceramic carrier is often done while the ceramic base is in a "green" non-dimensionally stable state. The procedure of dimensionally stabilizing the "green" ceramic carriers, called firing causes the ceramic base material to shrink in a somewhat predictable fashion.
Prior processes attempted to compensate for the predictable portion of the final dimensional uncertainty in surface feature location by processing the ceramic carrier and its features in a green state on an oversized scale. This process usually includes applying a conductive tungsten pattern which defines the contact pad locations to a green ceramic base, and then firing this assembly. Since the final contact pad location depends on their screened location and predicted amount of shrink, any uncertainty in this prediction will be in the finished carrier.
One known prior approach consists of applying a conductive tungsten pattern including tungsten contact pads then applying a ceramic slurry with openings which are smaller than the underlying contact pad areas and then stabilizing or firing all layers. After stabilizing the openings are filled with nickel plating and subsequently gold or other plating. This process does not eliminate dimensional uncertainty due to imperfect shrinkage estimates but is desired to prevent contaminates entering the tungsten-ceramic base interface region.